Transmission apparatus

ABSTRACT

The invention relates to a transmission apparatus in connection with a pulling equipment intended for moving especially a cable or a corresponding product, the transmission apparatus comprising a shaft that is operated by a motor ( 11 ) and that is connected to an output shaft ( 16 ) of the transmission apparatus by means of cog wheels ( 14 ). The output shaft ( 16 ) is connected to means ( 10 ) that are in contact with the cable. The cog wheels ( 14 ) are arranged to form a circle extending from the motor-driven shaft to the output shaft (16) and correspondingly from the output shaft ( 16 ) to the motor-driven shaft. In order to provide clearance-free operation, the cog wheels ( 14 ) are helical gearwheels, and one cog wheel shaft is arranged to be moved in its longitudinal direction when the rotation of the output shaft ( 16 ) is being decelerated.

The invention relates to a transmission apparatus in connection with apulling equipment intended for moving especially a cable or acorresponding product, the transmission apparatus comprising a shaftthat is operated by a motor and that is connected to an output shaft ofthe transmission apparatus by means of cog wheels, said output shaftbeing connected to means that are in contact with the cable or acorresponding product and that move the cable, the motor being arrangedto rotate the output shaft via the driven shaft and the cog wheels inthe direction of motion of the cable or the like and, if necessary, todecelerate the rotation of the output shaft in the direction of motionof the cable or the like, the cog wheels being arranged to form a circleextending from the motor-driven shaft to the output shaft andcorrespondingly from the output shaft to the motor-driven shaft.

In addition to cables, the phrase “a cable or a corresponding product”refers in the present application to ropes, conductors and otherproducts formed from strands, and to semi-finished articles of theproducts at different stages of production.

When sheathed cables are produced, the sheath must be vulcanized andcooled after the forming stage. For this purpose, the processing line isprovided with a vulcanizing tube that is followed by a cooling pipe inthe direction of travel of the cable. A metal conductor to be coated ispassed through the vulcanizing tube and the cooling pipe by means of afirst pulling equipment placed before the extruder and a second pullingequipment located after the cooling pipe. During the vulcanization, thecable is supported in the horizontal extruder process entirely by theaforementioned pulling equipments or by the first pulling equipment, thecooling pipe and the second pulling equipment. The cable travels along acatenary trajectory at least in the vulcanizing tube, which means thatat least the vulcanizing tube must be catenary in shape.

During the vulcanization process, the cable must not get into contactwith the hot vulcanizing tube, and therefore it is necessary that thecable is kept straight so that it does not touch the inner surface ofthe vulcanizing tube. If the cable touches the surface of thevulcanizing tube, the cable sheath will be damaged and the cable cannotbe used for the intended purpose. The aforementioned matters set greatrequirements for the operation of the pulling equipments. A pullingequipment, for example a drive wheel, must grip the metal conductorwithout any slipping between the conductor and the drive wheel, theframe of the pulling equipment must be very sturdy and firmly attachedto the bearing surface, the drive wheel must be firmly mounted inbearings to the frame in order to minimize the risk of vibration andoscillation, and for the same reason the transmission of the pullingequipment must operate as smoothly as possible without clearances. Theclearance-free operation of the transmission of the pulling equipment ishighly significant especially when loading takes place mainly in thedirection of motion, as for example in the cable vulcanization process,where the motor may get into decelerating action in connection withcertain cable sizes due to the tensile force of the cable. In otherwords, the motor may change its pole, whereupon the clearance of thegear transmission produces a tug, which easily results in harmfuloscillation of the cable.

In prior art pulling equipments, rotation of the drive wheel is based ona transmission apparatus that is formed of a gear rim and a cog wheeland that is placed between an actuator and the drive wheel. In sucharrangements, the drive wheel is provided with a gear rim that iscoaxial with the axis of rotation of the drive wheel and that compriseseither inside or outside gearing, and the pulling equipment is providedwith a motor-driven cog wheel. The speed of the motor is controlled bymeans of a sensor placed in the vulcanizing tube and used to measure thelocation of the sheathed cable in the tube. The pulling equipmentprovided at the output end of the cooling pipe is usually run at aconstant speed, and the location of the cable in the vulcanizing tube isadjusted by means of control of the rotational speed of the pullingequipment located before the extruder.

In practice, it has been noted, however, that despite very accuratemachining of the gear teeth, vibrations occur in the pulling equipmentin connection with the gear transmission described above, and thevibrations result in harmful oscillation of the cable in the vulcanizingtube. This is obviously a result of too big clearances between theteeth, the clearances becoming more evident with heavy loads. It shouldbe noted that in the present cable vulcanization lines the distancebetween the pulling equipments may be as much as 200 meters, which meansthat a hanging cable causes considerable loading in the drive wheel andthe teeth. A possible elliptical shape of the gear rim also causesvariation in the clearances of the teeth and therefore in the steadinessof the pulling.

In another prior art arrangement, the drive wheel is replaced withseveral closely positioned rollers that are mounted in bearings in asubstantially semicircular formation, and an inner endless rubber belttravels over the rollers. Outside the curved roller conveyor there is anouter endless rubber belt that passes over a sheave and presses againstthe roller conveyor in a semicircular form. The metal conductor to becoated travels between the inner and the outer belt to extruders. Thespeed of the metal conductor in the extruder is adjusted by deceleratingthe speed of the sheaves around which the inner belt travels. With thisarrangement it is possible to avoid the drawbacks resulting from theclearances of the gear transmission, but on the other hand, thedecelerating effect provided by means of the drive wheel issimultaneously lost.

Another essential drawback is that the inner rubber belt is subjected toa great pressure that is produced by the rollers and the outer rubberbelt and that tends to lead to a breakdown of the inner rubber belt.Another drawback is that the outer rubber belt tends to slide away fromthe drive groove and therefore breaks.

Another example of prior art arrangements is a caterpillar-type pullingmechanism, which is arranged in connection with a drive wheel that isfirmly mounted in bearings in the frame structure, the pulling mechanismbeing used to forward the metal conductor. On the one hand, such anarrangement improves for example the decelerating effect, but on theother hand, this kind of separate caterpillar equipment comprisesclearances, which cause problems with vibration as described above.

An example of prior art arrangements is a pulling equipment where theforce is conducted to the central shaft of the drive wheel by means of aworm gear. Such a gear is loaded with a high torque and therefore theequipment must be provided with a rather heavy construction, which alsomeans that it has often rather great clearances that also cause theaforementioned problems with vibration.

The purpose of the present invention is to provide a transmissionapparatus with which the prior art drawbacks, such as the vibrationproblems caused by the clearances of the transmission, can beeliminated. This is achieved with a transmission apparatus according tothe invention, which is characterized in that the cog wheels are helicalgearwheels and that one cog wheel shaft is arranged to be moved in itslongitudinal direction when the rotation of the output shaft is beingdecelerated, whereupon during the movement of the cog wheel shaft, thecog wheels situated on the shaft are arranged to rotate, due to oppositehelicity of the teeth of the cog wheels, the adjacent cog wheels thatare in mesh with the first cog wheels, thus eliminating the free playoccurring between the cog wheels during the deceleration.

The primary advantage of the invention is that the invention provideseven transmission that does not cause harmful vibrations in the cable ora corresponding product. Another advantage of the invention is itssimplicity, wherefore the start-up and use of the invention will beadvantageous.

The invention will be described in greater detail below by means of anembodiment shown in the accompanying drawing, in which

FIG. 1 is a perspective view of a cable coating line,

FIG. 2 is a general view of a pulling arrangement for a cable used inthe cable coating line,

FIG. 3 is a general view of a transmission apparatus according to theinvention,

FIG. 4 is a general view of the transmission apparatus of FIG. 3 seenfrom another direction,

FIG. 5 is a side view of an embodiment of the transmission apparatusaccording to the invention, and

FIG. 6 shows a detail of the embodiment of FIG. 5 seen from anotherdirection.

FIG. 1 shows a cable coating line. Reference numeral 1 denotes generallyconductor outputs, such as reels, from which the conductors are uncoiledand guided to the coating process. Reference numeral 2 denotes a pullingequipment, which may be a constant-speed capstan, for example. Referencenumeral 3 denotes an extrusion head with which a plastic sheath isformed on the structure consisting of the conductors. Reference numeral4 denotes in FIG. 1 a vulcanizing tube and reference numeral 5 denotes acooling section. Reference numeral 6 in turn denotes a pulling equipmentwith which the cable is pulled onto a take-up reel, which is denotedgenerally by reference numeral 7. The structure, details and operationof the cable vulcanization line of FIG. 1 are fully known to a personskilled in the art and therefore they will not be described in greaterdetail in this connection.

FIG. 2 is a general view of a pulling arrangement in a cablevulcanization line. Like reference numerals are used in FIGS. 1 and 2 todenote like parts. Further, in FIG. 2 reference numeral 8 denotesconductors that are uncoiled from an output reel 1 and reference numeral9 correspondingly denotes a cable, consisting of the conductors and asheath, that is guided to the take-up reel 7. In the embodiment of FIG.2, the pulling equipment 2 comprises a drive wheel 10, a motor 11 and atransmission apparatus consisting of gear transmission 12. The pullingequipment 2 also comprises control means 13 with which the speed of thecable in the vulcanizing tube 4 is kept constant so that the sheathsurrounding the conductors does not get in contact with the innersurface of the vulcanizing tube. The cable travels inside thevulcanizing tube along a catenary trajectory.

The problems of the prior art arrangements are related specifically tothe above-described pulling equipment since the transmission apparatusproduces vibrations in the cable, as stated above. The problem is mostapparent in the pulling equipment 2 of the vulcanization line, whereloads act mainly in the direction of motion of the cable. The vibrationsresult from the clearances of the transmission apparatus. The vibrationsmake the cable oscillate in the vulcanizing tube, whereupon the cable islikely to touch the inner surface of the vulcanizing tube, and thesheath will be damaged. The purpose of the transmission apparatusaccording to the invention is to provide an arrangement which enableseliminating problems that result from clearances of the cog wheels ofthe transmission apparatus, for example the above-described problemsoccurring in connection with the pulling equipment in the cablevulcanization line.

FIGS. 3 and 4 illustrate the basic principle of the transmissionapparatus according to the invention. According to the basic idea of theinvention, transmitting cog wheels 14 are arranged to form a circle thatextends from a shaft 15 operated by the motor 11 to an output shaft 16and correspondingly from the output shaft 16 to the shaft 15 operated bythe motor 11. Further, the cog wheels 14 are helical gearwheels, and onecog wheel shaft A is arranged to be moved in its longitudinal direction.As the shaft is moved, the cog wheels situated on the shaft are arrangedto rotate, due to the opposite helicity of the teeth of the cog wheels,the adjacent cog wheels 14 that are in mesh with the first cog wheels.This eliminates the free play between the cog wheels.

The movement of one cog wheel shaft A in its longitudinal direction isshown generally in FIG. 4. The shaft A is transferred by means of aforce F that is parallel to the axis of rotation of the cog wheelssituated on the shaft. The helicity of the teeth of the cog wheels isshown in FIG. 4 by means of diagonal lines drafted in the cog wheels.Moving the cog wheel shaft A by means of the force F makes the adjacentcog wheels which are in mesh with the cog wheels situated on the shaft Arotate around their axes of rotation. This rotational movement isdenoted by means of arrows N1 and N2. It is clear that the rotationalmovement according to arrows N1 and N2 also rotates correspondingly thenext cog wheels that are in mesh with the aforementioned cog wheels, andso on, the disadvantageous clearances being thus eliminated from theentire transmission chain. It is clear that the cog wheel 14 that ismoved can be any one of the cog wheels 14.

Referring again to FIG. 4, N1 and N2 may also be described as reactiveforces in that, when the force F is applied in a longitudinal directionat shaft A, resultant reactive forces N1 and N2 will be applied atadjacent cog wheels. Because only shaft A is moved longitudinally be theforce F, in this embodiment, free play between the teeth of the cogwheels is eliminated.

The above-described circle formed by the cog wheels 14 transmits therotating motion of the motor as shown by arrow M1 in FIG. 1, whereasopposite motion is transmitted as shown by arrow M2.

The force F that moves one cog wheel shaft A in the longitudinaldirection can be produced in any suitable manner. One advantageousmethod is to use a screw means to produce the force F. Such anembodiment is shown in FIGS. 5 and 6. The screw means is denoted in FIG.6 by reference numeral 17. The trajectory of the conductors 8 is shownin FIG. 5 by means of a broken line. In FIGS. 5 and 6, like referencenumerals refer to like parts as in FIGS. 1 to 4.

The transmission apparatus shown in the figures may also comprisedifferent sensor means that can be used to monitor and control theprocess. Examples of such means include a sensor means 18 which measuresthe loading tension of the gear or which measures the line tension of acable or the like. The sensor means 18 may naturally also be providedwith means that give an alarm if there are breakdowns in the run.

Even though the invention is described above in connection with aconstant-speed pulling equipment of a cable vulcanization line, theinvention is not restricted in any way to this embodiment. The inventioncan also be applied in other arrangements. The transmission apparatusaccording to the invention can also be used for example as a pullingequipment 6 in a vulcanization line. It should also be noted that theinvention is not restricted in any way to be used merely in connectionwith a pulling equipment utilizing a principle of a drive wheel, but theinvention can be applied in connection with different pullingequipments. Examples of different alternatives include various beltpulling equipments or caterpillar-type pulling equipments, and differentcapstans which have no belt and where the cable revolves 2 to 3 timesaround the reel. The invention can therefore be applied in connectionwith any equipment that is used on the line as a pulling equipment. Oneexample concerns spooling processes. Therefore, the invention is notrestricted in any way to a vulcanization process, even though theinvention does provide particular advantages in connection with such aprocess.

What is claimed is:
 1. A transmission apparatus in connection with apulling equipment intended for moving a cable or a correspondingproduct, the transmission apparatus comprising a shaft that is operatedby a motor and that is connected to an output shaft of the transmissionapparatus by means of cog wheels, said output shaft being connected tomeans that are in contact with the cable or the corresponding productand that move the cable, the motor being arranged to rotate the outputshaft via the driven shaft and the cog wheels in the direction of motionof the cable or the corresponding product and, if necessary, todecelerate the rotation of the output shaft in the direction of motionof the cable or the corresponding product, the cog wheels being arrangedto form a circle extending from the motor-driven shaft to the outputshaft and correspondingly from the output shaft to the motor-drivenshaft, wherein the cog wheels are helical gearwheels and wherein one cogwheel shaft is arranged to be moved in its longitudinal direction whenthe rotation of the output shaft is being decelerated, whereupon duringthe movement of the one cog wheel shaft, the cog wheels situated on theshaft are arranged to rotate, due to opposite helicity of the teeth ofthe cog wheels, the adjacent cog wheels that are in mesh with the firstcog wheels, thus eliminating the free play occurring between the cogwheels during the deceleration, wherein a force applied to the one cogwheel shaft in the longitudinal direction of the one cog wheel shaftmoves the cog wheel shaft.
 2. The transmission apparatus according toclaim 1, wherein the transmission apparatus comprises a sensor means formeasuring the loading tension of the gear.
 3. The transmission apparatusaccording to claim 1, wherein the transmission apparatus comprises asensor means for measuring the line tension of the cable or thecorresponding product.
 4. The transmission apparatus according to claim1, wherein the transmission apparatus is arranged in connection with thepulling equipment in a cable vulcanization line.
 5. The transmissionapparatus according to claim 4, wherein the transmission apparatus isarranged in connection with a constant-speed pulling equipment in acable vulcanization line.
 6. The transmission apparatus according toclaim 1, wherein a screw means applies the force.